Elamur Groupantsvfs-gates
The groupant beside vfs/tests/vfs.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.
Facts
Implementation material. A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.
Components
| component | label | where |
|---|---|---|
| approximant | partial | approximant |
| ast | partial | syntax.json |
| composition | partial | composition |
| cost | partial | Cost |
| descriptant | present | descriptant |
| invariant | partial | Invariant |
| tests | executed bounded checks | tests |
Obernants
The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.
| id | type | label | where |
|---|---|---|---|
behavior_complement | behavior_complement | partial source derived model | behavior_complement |
reverse_reconstruction | reverse_reconstruction | partial source derived model | reverse_reconstruction |
fixture_ownership | fixture_ownership | partial source derived model | fixture_ownership |
fault_oracle | fault_oracle | partial source derived model | fault_oracle |
snapshot_witness | snapshot_witness | partial source derived model | snapshot_witness |
partial_prefix_witness | partial_prefix_witness | partial source derived model | partial_prefix_witness |
Parts
Model text
descriptant
vfs-gates
Finite behavior gates and owned temporary fixture cleanup.
Prospective epoch
2026-10-31: source reviewed before edits; prospective review retained under $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31/prospective.md. Predicted order/cost: O(fixture bytes+tree work), maximum selected populate blob100000 bytes; four thread sandboxes in isolation test; no benchmark main.
Observation epoch
Bounded actual calls and compiled negative controls are recorded in tests.md. Production behavior bytes unchanged; only focused test blocks added. Snapshot constant-time wording is conditional on cwd and destruction; recursive operations may partially commit.
Unsupported approximants
No executable percentage surrogate is claimed for these categorical/state/effect observations. Future 1%,2%,5%,10% require a useful metric, explicit domain and exact reference.
approximant
Forward relation
Finite behavior gates and owned temporary fixture cleanup.
scratch creates TMPDIR/vfs-test-PID-name after best-effort removal; Drop best-effort removes own root. Tests instantiate bounded Vfs, DirFs and transfer fixtures; named gates compare expected result then inject Fault variants.
Domain: bounded inputs with available allocation and nonoverflowing counters unless checked explicitly. The relation is partial and source-derived.
composition
Composition
Finite behavior gates and owned temporary fixture cleanup. Shared state and order: scratch creates TMPDIR/vfs-test-PID-name after best-effort removal; Drop best-effort removes own root. Tests instantiate bounded Vfs, DirFs and transfer fixtures; named gates compare expected result then inject Fault variants.
Scoped children project this same source. Their domains and effects remain conditional; source execution connects these clauses rather than independently proving their wiring. Selected tests use only owned TMPDIR host data; absolute_paths_never_reach_the_host is excluded for actual /etc/passwd read; open_modes excluded for external nonexistent-root probe. Runtime Fault toggles are not compiled mutants.
models
Typed source models
Source-bound partial relations; no universal finite-test proof.
behavior_complement
Subject: vfs-gates. Domain: Finite behavior gates and owned temporary fixture cleanup. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Selected host fixture cleanup never intentionally targets outside dedicated TMPDIR; a passing finite gate does not establish universal confinement, allocation or concurrency semantics.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
reverse_reconstruction
Subject: vfs-gates. Domain: Finite behavior gates and owned temporary fixture cleanup. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Pass outcomes admit all implementations agreeing on finite fixtures, not unique implementation. Failed gate identifies violated observation but may admit many source defects.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
fixture_ownership
Subject: vfs-gates. Domain: Finite behavior gates and owned temporary fixture cleanup. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Scratch path combines fixed name and process id under dedicated TMPDIR. Same-process repeated names are sequential; cleanup errors ignored.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
fault_oracle
Subject: vfs-gates. Domain: Finite behavior gates and owned temporary fixture cleanup. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Five existing Fault checks require gates Err; compiled source mutants are a separate evidence class.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
snapshot_witness
Subject: vfs-gates. Domain: Finite behavior gates and owned temporary fixture cleanup. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: dump comparison observes state+counters but excludes journal, limits and fault; retained Arc bytes checked separately.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
partial_prefix_witness
Subject: vfs-gates. Domain: Finite behavior gates and owned temporary fixture cleanup. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: wave31 sparse fixture proves failed mkdir_all(/a/b) can leave /a, while checked write_at overflow leaves dump unchanged.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
tests
Checks and limitations
Exact named observations: escape_by_dotdot_is_denied, symlinks_cannot_lead_outside, bad_names_and_paths, limits_fire_with_clear_errors_and_leave_state_unchanged, limits_parse, snapshot_changes_restore_is_byte_identical, snapshot_is_isolated_copy_on_write, restore_after_failed_ops_and_limits, posix_like_semantics, virtual_clock_is_deterministic, journal_records_ops_errors_and_denials, import_export_round_trip, dirfs_confines_to_root, gates_green_and_negative_controls_red, wave31_sparse_copy_and_partial_directory_failure.
Fresh receipts: $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31; run.sh retains four profile/repetition sets with raw logs and numeric statuses. native-commands.json and source-test-map.json disambiguate targets. Compiled mutations and exact restoration are separately retained in mutation-summary.json.
These finite observations are not semantic completeness. Source syntax generated twice and compared byte-for-byte. Host effects are limited to owned TMPDIR fixtures. Existing absolute_paths_never_reach_the_host and open_modes are skipped; snapbench main is skipped. Standalone helpers/reexports are only observed through named callers or representation checks; RealFs effect methods unexecuted.
invariant-and-cost
Invariant and cost
Invariant
Selected tests use only owned TMPDIR host data; absolute_paths_never_reach_the_host is excluded for actual /etc/passwd read; open_modes excluded for external nonexistent-root probe. Runtime Fault toggles are not compiled mutants.
Cost
O(fixture bytes+tree work), maximum selected populate blob100000 bytes; four thread sandboxes in isolation test; no benchmark main.
No timing or numerical error guarantee is inferred from finite tests.
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